1. Field of the Invention
The present invention relates to an improved, reliable protective material for a semiconductor element, a semiconductor element provided with said protective material, and a semiconductor device provided with said semiconductor element. More particularly, the present invention relates to an improved, reliable protective material which can be disposed at the surface of a semiconductor element including a photoelectric conversion element such as a solar cell element, specifically, which is suitable for use as a surface covering material disposed on the light incident side of said photoelectric conversion element. The present invention also relates to a semiconductor element including a photoelectric conversion element such as a solar cell element which is provided with said protective material, and a semiconductor device provided with said semiconductor element.
2. Related Background Art
In recent years, societal concern for the problems relating to the environment and energy sources has been increasing all over the world. Particularly, heating of the earth because of the so-called greenhouse effect due to an increase of atmospheric CO.sub.2 has been predicted to cause a serious problem. In view of this, there is an increased demand for a means of power generation capable of providing clean energy without causing CO.sub.2 buildup.
Public attention has been focused on solar cells in order to meet such demand, because they can supply electric power without causing such a problem as above mentioned and are expected to be a future power generation source, and they are safe and easy to handle.
Such solar cells include single crystal silicon solar cells, polycrystal silicon solar cells, amorphous silicon solar cells (including microcrystal silicon solar cells), copper indium selenide solar cells, and compound semiconductor solar cells. Of these solar cells, various studies have been made on so-called thin film crystal silicon solar cells, compound semiconductor solar cells, and amorphous silicon solar cells since their semiconductor active layer can be relatively easily formed in a large area and in a desired form and they therefore can be easily produced at a relatively low production cost.
Particularly, thin film amorphous solar cells, specifically, amorphous silicon solar cells, comprising an electrically conductive metal substrate, an amorphous silicon semiconductor active layer disposed on said metal substrate, and a transparent and conductive layer disposed on said semiconductor active layer have been evaluated as being the most advantageous among the conventional solar cells because their semiconductor active layer comprised of amorphous silicon (hereinafter referred to as a-Si) can be easily formed in a large area and in a desired form on a relatively inexpensive substrate with a low production cost and they are light and excel in shock resistance and flexibility, and in addition, they can be designed into a solar cell module in a desired configuration which can be used as a power generation source.
Now, in the case of an amorphous silicon solar cell having a semiconductor active layer comprising, for example, an a-Si thin film disposed on a glass plate as a substrate, light is impinged through the substrate side, and because of this, the glass plate can be designed to serve as a protective member. However, in the case of the aforementioned solar cell having the a-Si semiconductor active layer disposed on the metal substrate, because the metal substrate does not permit incident light to transmit therethrough, light is impinged through the side opposite the metal substrate, and therefore, it is necessary to dispose an appropriate transparent protective member on the side through which light is impinged such that it protects the solar cell element.